Method of and control system for automatically correcting a pitch of a musical instrument

ABSTRACT

A pitch control system for the automatic pitch correction according to a harmony-dependent tuning, especially the harmonic tuning, for a musical instrument, having an input device for the input of note input signals in a pre-determined fixed tuning, especially the tempered tuning, and having a note generation device to which the note input signals are applicable, comprises a chord recognition circuit which ascertains at each input signal pattern corresponding to a chord whether this input signal pattern corresponds to a chord pattern from a pre-determined quantity of chord patterns, a signal pattern store circuit in which for each chord pattern of the pre-determined quantity of chord patterns a signal pattern is stored, and a control circuit which, when the chord recognition circuit ascertains that an input signal pattern is present corresponding to one of the pre-determined chord patterns, causes the signal pattern store circuit to emit the signal pattern, corresponding to the ascertained chord pattern, to the note generation device, for the production of the chord in each case in the variable tuning.

DESCRIPTION

The invention relates to a method of automatically correcting a pitch inaccordance with a harmony-dependent variable tuning, especially harmonictuning, of a musical instrument having an input device for the input ofnote input signals in a pre-determined fixed tuning, especially thesynchronously vibratingly tempered tuning, and having a note producingdevice to which the note input signals can be applied, with thefollowing steps:

a) in the case of an input signal pattern corresponding to a chord oneascertains, by comparison with pattern chords of a pre-determinedquantity of chord patterns, whether one of these chord patterns ispresent;

b) in the case of presence of a chord pattern the input signal patternis replaced by an input signal pattern corrected according to this chordpattern and is applied to the note producing device, while the signal ofthe signal patterns, allocated to a predetermined fundamental note ofthe respective chord pattern, is fixed according to the pre-determinedfixed tuning and the signals of the signal pattern allocated to theother notes of the chord pattern, starting from the fundamental note,are corrected according to the variable tuning.

A long existing problem of selecting a tuning consists in that when the"harmonically pure tuning", which is preferred in the course of playingof multiharmonic music and which indeed produces pleasant-to-hear chordsounds due to partial overlap of overtones and primary tones of thechord notes, is selected, the transition from one key to the other stillrequires a corresponding adaptation of the tuning (even within aharmonically tuned key there are chords having a frequency ratio notcorresponding to the harmonically pure tuning). In order, in the case ofinstruments which cannot vary their tuning during playing (for examplethe keyboard instruments pianoforte or organ), to render possibleplaying in various keys and the modulation from one key to the other,these instruments are tuned in a pre-determined fixed tuning in whichthe chords sound more or less equally well (or equally badly) in thekeys which come into question. One example for such a fixed tuning isthe tempered tuning according to Johann Sebastian Bach. However otherfixed tunings have also been proposed, especially the baroque tunings"Werckmeister" and "Kirnberger" (see DE-PS 2,558,716) which preferspecific chords or keys, but at the cost of other chords or keys.

It is known from DE-A 3,304,995 to provide an electronic keyedinstrument with tonality selection keys for manual operation duringplaying, actuation of which has the consequence that the keyedinstrument is instantaneously harmonically purely tuned with regard tothe selected tonality (for example C major sub-dominant). This manualactuation disturbs the flow of playing and further presumes that theplayer immediately recognises the tonality in each case during playing.

From DE-A 3,545,986 an electronically controlled musical instrument isknown which examines successive notes as to whether they can beallocated to a key. If this is the case, next the instrument isharmonically purely tuned to the corresponding key, for example C majoror E minor. For the unequivocal identification of the respective key theseven notes of an octave are needed. Thus under some circumstances thekey identification takes place only after relatively long playing, ornot at all. If thereafter a piece of music begins anew or a modulationor a shift takes place, the struck chords then do not sound harmonicallypure. Even remote-key passing-notes, such as ornamentations or chromaticpassages, cause such an instrument temporarily to cause the tonallyspecified harmonic tuning and to tune harmonically purely to the oldtonality or possibly a new tonality only after a waiting time. Likewisesuch an instrument does not tune to a key, or constantly changes tuning,if multi-part music sounds which cannot be fixed to a major or minorkey.

From DE-B 3,023,578 a circuit arrangement for the identification of thechord type and its fundamental note is known which serves to produce anautomatic accompaniment to a melodic part played on the instrument.WO-A-80/00110 likewise shows a circuit arrangement for chord recognitionwith the possibility of causing the whole chord to sound by pressing ofthe key allocated to a chord fundamental note.

From U.S. Pat. 4,248,119 a method of the initially stated kind is knownin which, after identification of the chord in each case, the chordnotes are corrected in relation to the chord fundamental note in such away that harmonically pure chord tuning results. The chord fundamentalnote is here not corrected, that is it corresponds to the pre-determinedfixed (synchronously vibratingly tempered) tuning. With this knownmethod thus harmonically purely tuned chords result. However it has beenrecognised that different chords played in immediate succession cansound unpleasant, especially when the same notes occur in the twochords, but in different function. By reason of the frequencycorrection, which in each case is specific to the chord and thereforedifferent, of these notes, in the two chords they lie at differentpitches, which is felt unpleasant in the case of correspondingly greatfrequency difference.

In comparison therewith, the object of the invention consists inproviding a method of the initially stated kind with which it ispossible to achieve a further sound improvement.

This object is achieved by additionally correcting the signal of thesignal patterns allocated to the fundamental note, in relation to thepre-determined fixed tuning, and correcting the signals of the signalpattern, allocated to the other notes of the chord pattern, startingfrom the corrected fundamental note, according to the variable tuning,correcting the signal allocated to the fundamental note of a chord, insuch a way that the correspondingly corrected note delivered by the noteproducing device lies higher or lower than the fundamental note in thepre-determined fixed tuning, according to whether the chord notes,corrected according to the signal pattern, lie lower or higher onaverage than the uncorrected chord notes in the fixed tuning.

This measure according to the invention results in a kind ofequalisation successive chords, with the consequence that the frequencydifferences of equal notes are reduced. Successive chords soundnoticeably better.

Preferably the signal allocated to the fundamental note of a chord willbe corrected in such a way that the displacement of a mean frequency ofthe chord notes is at least approximately compensated, on the basis ofthe correction of the chord notes by the signal pattern. In the case ofuse of correction signals stating relative frequency variations it isproposed that the signal allocated to the fundamental note of a chord iscorrected with an additional correction signal stating a relativefrequency variation, which signal corresponds in value, but withreversed sign, to the mean value of the correction signals, likewiseindicating relative frequency variation, for the input signals.

By this additional correction notes of like name in chords, which can berepresented as stages of one single key, are retuned only so far thatthis retuning lies below the audibility limit. An example would be thenote E in D major, as third of the stage I, C-E-G, as fundamental noteof stage III, E-G-B or as fifth of stage VI, A-C-E. Thus akey-independent but key-compatible retuning takes place.

Special attention must be accorded, in the case of small major seventhchords, to the note with the function of the small seventh in the chord.In tempered tuning this note has the value of 1000 cents in relation tothe fundamental note of the chord. In historic time the small seventh ofa scale was often tuned to the value 7/4 in relation to the fundamentalnote, which corresponds to the frequency ratio of the 7th harmonic of anatural note sequence. However this value is useless for present-daypractical music-making, since with 969 cents it is too remote from thevalue of the tempered tuning.

The frequency ratio as it occurs in the dominant seventh chord within aharmonically tuned major scale offers a usable value. In the dominantseventh chord the fundamental note is formed by the fifth of therelevant key, while the small seventh is formed by the fourth of theoctave lying thereabove. The fifth has a frequency ratio of 3/2 relationto the fundamental note of the key, the fourth lying thereabove of thenext octave has a ratio of 2×4/3=8/3 to the fundamental note of the key.Thus the small seventh of the dominant seventh chord is in theproportion to its fundamental note as 8/3:3/2=16/9. This corresponds to997 cents to the chord fundamental note. After execution of thealready-mentioned additional correction this note in the small majorseventh chord results in a correction of preferably +1 cent to thefrequency of the tempered tuning, which sounds well.

In the case of a small minor seventh chord on the other hand the notewith the function of the small seventh in the chord has the usual valueof 6:5 to the fifth, which corresponds to a spacing of 1018 cents to thefundamental note.

In order to have to effect only a chord pattern comparison in the12-note space corresponding to one octave, it is proposed that the inputsignal pattern is projected on to a pre-determined octave (definitionoctave) and compared with the chord patterns, likewise each limited toone octave, of the pre-determined quantity of chord patterns.

This comparison can be effected, in a first alternative, in that theinput signal pattern is displaced as a whole by half-notes within thedefinition octave, and the displacement steps are counted, until asignal lies at a pre-determined end of the definition octave, and thatthe signal pattern shifted in this way is compared with the chordpatterns of the pre-determined quantity of chord patterns, where amongthe chord patterns a chord note in each case likewise lies at thepre-determined end of the octave.

It is however also possible to proceed in a manner in which the chordpatterns of the pre-determined quantity of chord patterns are shifted byhalf-notes cyclically within the octave, counting the shift steps, andthe chord patterns shifted in this manner are compared each with theunshifted input signal pattern. The first alternative has the advantagethat one makes a small number of displacement steps suffice. The secondalternative has the advantage that one has only to compare one singlechord pattern per chord type, even though with longer calculation time,whereas in the case of the first alternative, for example in the case ofa major triad, three chord patterns in all, allocated to this triad,have to be compared with the input signal pattern.

In order, when one of the chord patterns is present, to be able toreplace the input signal pattern by a correspondingly corrected inputsignal pattern, to the chord patterns of the pre-determined quantity ofchord patterns there are allocated signal patterns which either canalready correspond to the corrected input signals (for example bystatement of the note frequency in each case, or which, preferredly,form correction signals for the input signals.

So that the signal patterns allocated to the chord patterns can likewisebe limited to one octave it is proposed, for the simple consideration ofthe initial displacement of the input signal pattern and/or the chordpatterns, that in the case of conformity of the input signal patternwithin the definition octave with a chord pattern of the pre-determinedquantity of chord patterns one charges a signal pattern, allocated tothe chord pattern concerned and limited to one octave, into an outputstore and shifts the signal pattern according to the number ofdisplacement steps by half-notes in the output store in the oppositedirection, possibly cyclically. The direction of displacement is thusopposite to the initial displacement of the input signal pattern or thechord patterns. In the case of cyclic displacement of the chord patternswithin the octave, that is with feeding of the store content from theoverflow end of the store to the other store end, a cyclic displacementin the opposite direction takes place correspondingly in the outputstore. The correction signals then stand in the corresponding positionof the octave, so that now only the input signals, irrespective of inwhich of the possible octaves they stand, are to be corrected. Thecorrection signals relate preferably to relative frequency variations,especially stated in cents, in order to achieve independence of theoctaves.

An especially preferred further development of the method according tothe invention is characterised in that after ascertaining an inputsignal pattern corresponding to a chord pattern, one ascertains amongthe following input signal patterns whether the corresponding note ornotes of the input signal pattern is or are contained completely in thechord pattern and if so one corrects this note or these notes accordingto the chord pattern. This measure offers the advantage that directlyafter the playing of a chord from the quantity of the pre-determinedpatterns, and its sounding in harmonic tuning, individual notes orcombinations of individual notes of this chord can also be played,without the tuning of these notes changing. This is very advantageous iffor example a chord is played to a choir for intonation, and then theindividual notes of this chord are to be played to the choir.

In further development of this measure it is proposed that additionalchord notes are allocated to the pattern chords and that on ascertainingan input signal pattern corresponding to a chord pattern among thefollowing input signal patterns one ascertains whether the correspondingnote or notes of the input signal pattern correspond to additional chordnotes of the ascertained chord pattern, and if so corrects this note orthese notes according to the additional chord notes. These chordadditional notes are notes which downwardly or upwardly adjoin thepattern chord. Large or small thirds are preferredly provided, where alarge third of the pattern chord is adjoined by a small third for theadditional chord note, and vice versa. Thus in the case of a major triadan additional chord note adjoins downward at the interval of a smallthird and an additional chord note adjoins upwards at the interval of alarge third.

In the case of a multi-manual input device it is proposed that for eachmanual separately the respectively associated input signal pattern iscompared with the chord patterns of the pre-determined quantity of chordpatterns. Since in general accompaniment chords are played on one of themanuals, these can be identified even when chord-foreign notes, forexample what are called passing notes, are being played on anothermanual.

It is further proposed that after ascertainment of an input signalpattern corresponding to a chord pattern, on one of the manuals, thefollowing input signal patterns of all manuals are examined as towhether the corresponding note or notes are completely contained in thechord pattern. Thus the chord-identical notes of all manuals arecorrected, while the notes not pertaining to the ascertained chordpattern retain the frequencies of the tempered tuning.

In place of or in addition to the proposed additional correction of thefundamental note frequencies of the chords, to avoid ill-soundingfrequency differences of equal notes of successive chords, it isproposed that, in two successive input signal patterns which correspondeach totwo successive chord patterns of the pre-determined quantity ofchord patterns, one ascertains whether the same note occurs in bothchord patterns, and if this is so one effects such an additionalocrrection in the second input signal pattern that the conforming notesin the two chords possess substantially the same level or at least afrequency differencenot exceeding a pre-determined value of preferablyless than 8 cents. If this additional correction concerns only theconforming note, then correspondingly there results a slight deviationof this note from the variable tuning in the second chord. It is howeveralso possible to let this additional correction pertain to all notes ofthe new chord, so that a shift of all notes of this new chord towards"higher" or "lower" occurs. Thus the frequency ratios of the variabletuning will be retained. Since such a shift towards "higher" or "lower"could occur in exceptional cases a number of times in succession in thesame direction, it is preferably provided that this additionalcorrection be limited, preferably to a value below 16 cents in onedirection in total.

The invention also relates to a pitch control system for a musicalinstrument for carrying out the method as described above, with an inputdevice for the input of note input signals in a pre-determined fixedtuning, especially the synchronously vibratingly tempered tuning, andhaving a note producing device, to which the note input signals areapplicable, comprising

a chord recognition circuit, which at every input signal patterncorresponding to a chord ascertains whether this input signal patterncorresponds to a chord pattern from a pre-determined quantity of chordpatterns,

a signal pattern store circuit (34) in which a signal pattern is storedfor every chord pattern of the predetermined quantity of chord patterns,including a signal allocated to one pre-determined fundamental note ofthe chord pattern in each case, a control circuit which, when the chordrecognition circuit ascertains that an input signal patterncorresponding to one of the pre-determined chord patterns is applied,causes the signal pattern store circuit to deliver the signal pattern,corresponding to the ascertained chord pattern to the note generationdevice, for the generation of the respective chord in the variabletuning, the fundamental note of the chord being corrected in relation tothe pre-determined fixed tuning and the other notes of the chord,starting from the corrected fundamental note, being corrected accordingto the variable tuning.

As signal patterns stored in the chord pattern store circuit, signalsdirectly corresponding to the desired chord in the variable tuning, forexample stating their frequency, can be stored. It is however especiallypreferred that correction signal patterns are stored as signal patternsin the chord pattern store circuit, for the correction of the note inputsignals according to the variable tuning, and that a correction circuitis provided to which the note input signals and the correction signalsof the correction signal patterns are applicable, and which delivers, asoutput signals, the note input signals corrected in accordance with thecorrection signals, to the note producing device. This form ofembodiment of the invention leads to a simplified construction of thecontrol system, especially because it permits a reduction in the storerequirement of the chord pattern store circuit (12 storage places percorrection signal pattern).

In order to facilitate the progress of the method in the chordrecognition circuit too, with reduced store requirement, it is proposedthat a definition octave store is provided having 12 storage placeswhich are allocated to the 12 different notes of a pre-determinedoctave, where in the examination of an initial signal patterncorresponding to a chord a storage place is occupied when the notecorresponding to this storage place occurs in the chord in any desiredoctave. By reason of this projection of the input signal pattern on tothe definition octave it is merely necessary to work withcorrespondingly reduced quantities of information.

It is further proposed that a work store is provided having 12 storageplaces, into which the stored content of the definition octave store istransferrable, and a shift counter which, starting from the countervalue "0", is increased by "1" each time when the stored content of thework store is shifted by one storage place in a predetermined direction.

Correspondingly, a chord pattern store can be provided having in eachcase a storage line allocated to one of the chord patterns of thepre-determined quantity of chord patterns, especially with 12 storageplaces in each case. By reason of the mentioned projection of the inputsignal pattern on to the definition octave the chord patterns to becompared therewith can likewise be limited to one octave (12 storageplaces). In the case of formation of the work store as shift registerstore it is possible to shift the store content concerned in thepre-determined direction until an occupied storage place correspondingto a chord note has arrived at the corresponding end of the work store.With the input signal chord "marginally adjusted" in this manner then insequence the likewise "marginally adjusted" chord patterns from thechord pattern store are compared.

Furthermore a chord store can be provided having 12 storage placesallocated to each note of an octave, for the storage of the lastrecognised chord. This gives the possibility of abstaining from thechord pattern comparison, if the same chord is played a number of timesin succession. Moreover this comparison of the played notes with thechord store offers the advantage that the frequency of the notes doesnot change if, following upon a recognised and frequency-correctedchord, chords from a partial quantity of the notes of the precedingchord or even individual notes of this chord are played.

It is further possible for a correction factor store to be provided,having storage lines, especially having in each case 12 storage placesallocated to each of the 12 different half-notes of an octave, which areallocated each to a chord pattern of the pre-determined quantity ofchord patterns.

It is further proposed that an output store is provided, especiallyhaving in each case 12 storage places allocated to each of the 12different half-notes of an octave, into which the content of the storageline, allocated to a recognised chord, of the correction factor storecan be transferred, and the stored content of which is displaceablepreferably in a pre-determined direction. Thus it is possible in asimple manner to take account of the marginal adjustment, effected tofacilitate the chord pattern comparison, in the issue of the correctionfactors, by appropriate shifting back in the output store.

The invention will be explained hereinafter by reference to Tablesdesignated by I-VI at the end of the description and with reference tothe drawing.

Table I indicates the designation of the function of the notes of aseries of selected chords in the representation as selected here;

Table II indicates the frequency ratios of the notes of a chord, inrelation to one another, namely both in the harmonic tuning and in thetempered tuning;

Table III shows a list of the chords to be corrected, with theassociated correction values;

Table IIIA shows a list according to Table III, with modified correctionvalues;

Table IV indicates for each of the selected chords the associated chordpattern stored in the chord recognition store;

Table V allocates the chord pattern numbers according to Table IV to thenote examples according to Figure III;

Table VI shows the effect of a chord pattern shift by half-notes.

FIG. 1 shows a musical example (transition from an E minor chord to a Cmajor chord) with table for the explanation of the additionalcorrection.

FIG. 2 shows a greatly simplified circuit diagram.

FIG. 3 shows a series of musical examples designated by a-n.

FIG. 3a shows further notational examples and

FIG. 4 shows the occupation of a series of stores used for the methodaccording to the invention.

FIG. 5 shows the upper half of a flow diagram.

FIG. 6 shows the lower half of the said flow diagram.

In the method for pitch control according to the invention as describedin detail below commencement will be made from a fixed tuning whichcorresponds to the tempered tuning with division of an octave into 12equal half notes, that is with a frequency ratio of ¹² √2 correspondingto 100 cents. However other fixed starting tunings are also conceivable,as for example the tunings as stated in DE-PS 2,558,716. In order thatdifferent keys may be played and key modulations may also be executed,in the case of instruments which, in contrast for example to bowedinstruments and wind instruments, cannot be retuned by the player duringplaying, it is necessary to effect such a fixed tuning, as in keyedinstruments pianoforte and organ (pipe or electronic). According to theinvention now for instruments which permit multi-part playing and thusthe playing of chords, now a frequency correction of the notes should beeffected in such manner that the chords are harmonically purely tuned.For this purpose the instrument must comprise a note generation devicewhich permits the production of frequency-corrected notes. Thispre-requisite is provided from the outset in "electronic organs" or"synthesisers". However it is also conceivable to use a pipe organ inwhich several pipes of different pitch (for example length) areallocated to each individual note, with actuation according to choice ofthe pipe desired in each case. A pipe organ can also be used in whichpipes with variable pitch (for example variable length) are used inorder to render possible the desired retuning of the pipe duringplaying.

Table V indicates those chords which are proposed for the harmonicallypure tuning, where according to the utilisation case less importantchords can be dropped or further chords can be added. Furthermore chordswith more than four different notes will be disregarded in the exampleof execution. All chords will be recognised and corrected not only intheir basic position according to Table I (fundamental note G as lowestnote), but also in all reversals, positions and duplications. This isachieved in that all notes from all octaves are projected on to oneoctave, designated as "definition octave", consisting for example of the12 succeeding half notes from c' to b'. If for example the three chordsof the example a according to FIG. 3 are considered, then in the C majorchord designated by a1 the note C is the lowest note, if it is projectedon to the definition octave from c' to b', the note E is the next higherand the note G the highest on this definition octave, so that this chordis represented on the definition octave exactly as reproduced, and canbe identified by chord pattern No. 1 according to Table IV. The chord a2is an A flat major triad, in which its notes, projected on to the saiddefinitive octave, would be read from below upwards in the sequence C, Eflat and A flat, which conforms with the chord pattern No. 2 accordingto Table IV. Accordingly the F major triad as example a3 is read frombelow upwards in the sequence C, F and A and corresponds to the chordpattern No. 3 of Table IV.

The played chords thus appear, in projection on to the definitionoctave, in their basic position or in one of their reversals,irrespective of in which position, duplication or reversal they areplayed. The position of the chord in the definition octave does not haveto correspond to the position in which the chord is played, but dependsupon the initial and final notes of the selected definition octave andupon of which concrete notes the chord played in each case consists. Asfurther appears from Table IV, by reference to the representation of thenotes on the definition octave and of the specific pattern of each chordit is possible to determine the function of the individual notes of thechord (here represented as letters G, M, T, Q, R and S according toTable I) and thus a quite specific correction value of tempered toharmonic tuning can be allocated to each note with a specific functionin the chord.

By reference to FIG. 2 in combination with Table II it is to bedemonstrated that audible discords can occur even in the case ofindividually harmonically pure tuning of successive chords. At the topin FIG. 1 there is represented the transition from an e minor triad to aC major triad. In order to have a fixed reference system, by way ofexample the chord note in each case is fixed in the function G in thefixed (tempered) tuning, that is at the fundamental note e (=330 Herz).The notes g (with function M) and b (with function Q), which accordinglyin the case of tempered tuning (see Table II) would have frequencies of392 (=300 cents) and 494 Herz (=700 cents), are then corrected to thefrequencies 396 Herz and 495 Herz. Accordingly the fundamental note c(with function G) of the C major chord is fixed at 523 Herz with theharmonic frequencies 392 and 327 for the lower notes e (with function Q)and g (with function T).

If now one compares the two lowermost notes of the two chords, whichboth correspond to the same note, namely the note e. these notes, playedin immediate succession, due to the correction to harmonic tuning have afrequency difference of about 1%. This is also valid for the two middlenotes of the chords with 396 and 392 Herz respectively. Such a frequencydifference of inherently equal notes played in immediate succession isaudible and will be felt to be unpleasant.

In order to avoid this effect, the major triads, harmonically tuned asbefore, are shifted as a whole to higher frequencies and accordingly theminor triads, tuned harmonically purely as before, are shifted to lowerfrequencies. According to Table III a frequency shift of the majortriads upwards by 4 cents and a frequency shift of the minor triadsdownwards by 6 cents has proved especially advantageous.

On the basis of this additional correction the frequency difference ofthe relevant notes now lies with 1 Herz in each case, below 1/3% andaccordingly is no longer audible.

In Table III in the third column from the right the preferred additionalcorrections for the stated chords are listed.

In Table III A there are stated alternative additional corrections for aseries of chords which are distinguished by improved fifth purity.

FIG. 2 shows a purely diagrammatic circuit diagram for the explanationof the method. An input device 10 for the input of tone input signals inthe fixed tuning is symbolised as a row of piano keys 12 for theactuation of switches 14 allocated to each key 12. The leads 16 issuingfrom the switches 14 are combined into a collective lead 18. A notegenerating device 20 comprises a note signal output circuit 22, which ingeneral is provided with note frequency generators, and through a lead24 actuates one or more loudspeakers 26. In place of the loudspeaker 26it is also possible for a recording apparatus, for example an acoustictape, to be provided for "interim music storage". The lead 18 enters achord pattern recognition circuit 28, from which again a lead 30 issuesfor connection of the circuits 28 and 22. The input device 10 and thenote generation device 22 correspond in construction and function to thecorresponding components of conventional electronic keyed instruments.

The chord pattern recognition circuit 28 is connected through a lead 31with a control circuit 32 which again is connected through a lead 33with a signal pattern storage circuit 34. The control circuit 32 isadditionally connected through a lead 35 with the note signal outputcircuit 22.

The general function of the circuit arrangement according to FIG. 2 isthe following:

The note input signals are fed through the lead 18 to the chordrecognition circuit 28. The chord recognition circuit examines whetheran input signal pattern corresponding to a chord and consisting ofseveral different notes corresponds to a chord pattern from apre-determined quantity of chord patterns. If this is the case, thenthis is notified to the control circuit 32 which calls forth thecorrection signals allocated to this chord and forwards them through thelead 35 to the note signal output circuit 22, which accordingly correctsthe note input signal fed to it through the lead 30 and delivers them ascorrected output signals to the loudspeaker 26.

The method as described is naturally not limited to such an electriccircuit arrangement, but can also be realised by appropriatelyprogrammed programme-controlled equipment.

In FIGS. 4 and 5 a corresponding programme progress is represented,again purely diagrammatically. The stores mentioned in the programmeprogress diagram are explained in greater detail in FIG. 4. A definitionoctave store 40 is seen having twelve storage places 42, which insequence each comprise a half note of the scale, for example beginningat the note c. A chord store 44 has the same construction. A work store46 likewise comprises twelve storage places; however the work store 46is formed as shift register store, so that the storage places are merelynumbered through from 1 to 12 and not allocated to any note of thescale. A shift counter 48 is allocated to the work store 46 and countsthe shift steps, each by one storage place corresponding to a half noteof the scale, executed in each case.

A chord recognition store 50 comprises storage lines 52 allocated eachto one of the chord patterns according to Table IV, each with twelvestorage places 54. As appears from a comparison, for example of thefirst four storage lines, with the Table IV chord patterns Nos. 1-4, thestorage place occupation in the chord recognition store 50 correspondsto the chord patterns. For the chords proposed here for correctionthirty-nine lines 52 are provided.

A correction factor store 56 is likewise organised in thirty-nine lines58 each of twelve storage places 60. While in the chord recognitionstore there stands, according to the chord pattern in each case, eithera "1" (that is chord note) or a "0" (that is no chord note), in thecorrection factor store 56 at those storage places which correspond tothe corresponding storage places provided with "1" in the chordrecognition store 50 the correction signals allocated to the respectivenote according to Table III are stored. These correction signalscorrespond in each case to the total correction in cents from the secondcolumn from the right of Table III. If for example one considers thethird line in the correction factor store 56, which is allocated tochord pattern No. 3, then the number "6" is stored in the first storageplace--this because this note, according to Table IV, corresponds infunction to the note with the function Q (=fifth), to which note again,according to Table III, uppermost line, a correction of +6 cents isallocated. The storage places 60 of the store 56, which correspond inlocation to the storage places 50 occupied with "0", are likewiseoccupied with "0".

Finally an output store 62 is also provided again having twelve storageplaces, which are numbered in order to indicate that this store too isformed as shift register store.

In the case of the circuit arrangement principle as shown in FIG. 2 thestores 40, 44, 46 and 50 can be allocated to the circuit 28, the store56 to the circuit 34 and the store 62 to the circuit 32.

The progress of the programme or method appears from FIGS. 5 and 6.Commencing from the starting block 70, it is tested in the nextsucceeding decision block 72 whether the input signals delivered by thenote production device 10 are unchanged, that is whether the momentaryswitch condition remains further, that is for example one or more keysare unchangedly pressed. If this is the case, the programme jumps to theblock 74, to be explained later, and then to the "return block" 76. Theresult is the unchanged output of the input signals corrected ashitherto, to the note production device 20, so that the notes justplayed continue to sound in unchanged tuning.

If on the other hand the input signals are changed, the input signalpattern is charged according to a block 84 into the definition octavestore 40, namely in a manner in which then for example the store line 42allocated to the note c is occupied with "1", if one or more keys eachallocated to the note c in any octave are pressed. Incidentally thestorage places receive the store content "0". Thus in the result notesof like name of any desired octaves are linked by the logic function"or", so that the desired projection of the introduced chord on to thedefinition octave is obtained.

In the subsequent block 86 it is examined whether the chord now struckconsists exclusively of chord notes of the chord last struck andrecognised as chord pattern. If this examination in the decision block88 shows that a pure repetition is present, then to shorten the method amove is made to the block 74, with the result that the new chord soundswith the frequency corrections in accordance with the chord last played,and the new "chord" can consist of only one single chord note of thepreviously played chord recognised as chord pattern.

If however the new chord differs in at least one note from thispreviously played chord, then the programme steps further to a decisionblock 89, in which it is examined whether the input signal patterncorresponds only to one single note If this is the case the programmegoes over to a block 80 in which the already mentioned output store 62is cleared, just like the chord store 44 in a subsequent block 82,whereupon the programme proceeds again to a block 74 for the output ofthe input signal corresponding to the single note to the note generationdevice 20, namely without correction, since the correction factors areset to "0" in the output store. Thus the single note sounds in temperedtuning.

If on the other hand it is ascertained that the input signal patterncorresponds to several notes, then the content of the definition octavestore 40 will be charged according to a block 90 into the work store 46.The shift counter 48 is set in an adjoining block 92 to the number "0".The next programme loop serves to shift the store content of the workstore until a "1" has arrived at for example the left edge of thestorage line of shift register type which forms the work store 46. Thiscan also be designated as marginal adjustment. In this way thecomparison with the chord patterns in the chord recognition store is tobe facilitated, since the content of the corresponding lines 52 of thisstore 50 is likewise marginally adjusted, as may be seen from FIG. 4.

In a decision block 94 following upon the block 92 it is examined inthis connection whether a "1" is situated in storage line No. 1 of thework store 46. If this is not the case, the programme advances to ablock 96, in order to shift the content of the work store 46 one line(corresponding to a half note) to the left. At the same time in theblock 98 the store value of the shift counter 48 is increased by "one".Next the programme returns to the decision block 94. The loop formed inthis way is run through until the marginal adjustment is achieved, thatis a "1" is stored in the store line 1.

The programme then proceeds to a block 100 (FIG. 6). In that action thechord recognition store 50 is actuated, namely its first line with thechord pattern No. 1. In the following programme loop the marginallyadjusted content of the work store 46 is compared in sequence with allchord patterns, until either equality with a specific chord pattern hasbeen ascertained or until all chord patterns have been taken throughwithout conformity. In one block 102 of the loop the chord recognitionpattern in reach case is compared with the content of the work store. Ina subsequent decision block 104 a transfer is made to a next-succeedingdecision block 106 within the loop, if the momentary chord recognitionpattern does not correspond to the content of the work store. In thedecision block 106 it is tested whether all the chord patterns havealready been examined. If this is not yet the case, that is the actualchord pattern number is less than the maximum chord pattern number (39in the example according to FIG. 4), then the programme passes to ablock 108 in which actuation of the next succeeding line of the chordrecognition store 50 is instigated. Then the programme returns to theblock 102, within this loop.

If in the decision block 104 on the other hand it is ascertained thatthe played chord corresponds to a pattern chord, that is the content ofthe work store corresponds fully to that of a store line of the chordrecognition store, the programme leaves the said loop and passes overfrom the decision block 104 to a block 110 according to which thecontent of the chord store 44 is actualised by take-over of the contentof the definition octave store 40. A block 112 follows, according towhich that storage line of the correction factor store 56 is actuatedthe number of which corresponds to that of the momentarily actuated lineof the chord recognition store 50, that is the number of that chordpattern, which has been ascertained as identical with the momentarilyplayed chord. This line is copied into the output store 652 in asubsequent block 114.

In correspondence with the chord recognition store 50, the contents ofthe store lines 58 are also marginally adjusted in the correction factorstore 56. In order that the marginally adjusted correction factorsascertained in this way may be allocated in the note production to theplayed chord notes in their unshifted position, the marginal adjustmentof these correction factors in the output store 62 is reversed. For thispurpose there serves a programme loop following the block 114. Followingupon the block 114, as part of the loop, a decision block 116 isapproached, where it is tested whether a marginal adjustment in the loopformed by the blocks 94, 96 and 98 should have been effected. In thecase of the chord marginally adjusted from the outset in the definitionoctave store (that is in the case of a played chord containing the notec, if the definition octave commences with the note c), a shift in thework store is naturally not necessary. In the latter case the shiftcounter would still have the value "0". If this is not the case, then inthe loop the block 116 is followed by a block 118, according to whichthe store content of the output store 62 is shifted to the right, thatis to the next higher line number. Thereupon in a block 120 the value inthe shift counter is reduced by one. Then the programme loop returns tothe decision block 116. Thus the loop is run through until the shiftcounter has the value "0", so that as a result the correction factorsstand in the output store at the same position as the notes of thedefinition octave.

Regarding the storage place occupation of the output store 62 it shouldbe added that when for example it is ascertained that chord pattern No.4 is present, the output store accordingly has F=0 at each of thepositions 2, 3, 5, 6, 7, 9, 10, 11 and 12, and at position 1 F=-6, atposition 4 F=10 and position 8 F=-4. F=0 signifies that no pitchcorrection is to be effected at the note concerned, that is this soundsin tempered tuning. Otherwise the note will be corrected according tothe stated correction factor (in cents).

Since the initial displacement is merely reversed within the octave ofthe work store (in the loop with the blocks 94, 96 and 98) later in theloop 116, 118, 120 within the octave of the output store (with identicalchord pattern), there is no danger of the output store overflowing, thatis a correction factor different from zero being pushed out of thestore.

It is however also conceivable to effect the chord recognition in amanner in which for each chord there is used a single chord pattern, forexample chord pattern No. 1 for the major triad, which then iscyclically displaced in a shift store with twelve storage places, sothat thus chord patterns 2 and 3 are also present in the interim (chordpattern 2 results for example on a cyclic displacement of chord patternNo. 1 in Table IV to the left by four half-notes). Then for each chordthe one chord pattern must be shifted by a complete cycle (12 steps) andcompared each time with the played chord, a marginal adjustment of thischord being unnecessary. With this procedure then the output store wouldhave to be correspondingly cyclically organised with displacement in theopposite direction, according to the number of shift steps necessaryuntil conformity of the chords.

Reference is to be made briefly to Table VI, from which it is to be seenthat (in the case of a definition octave beginning with the note c) aplayed E-major triad requires four shift steps to the left in the workstore 46 before the marginal adjustment is achieved. Accordingly thenthe store content of the output store 62, corresponding to line No. 4 ofthe correction factor store 56, must be shifted by four steps to theright, so that then for example the correction factor "-6 cents" standsat the storage point allocated to the note e.

After the execution of the necessary displacements in the output store(value in the shift counter=zero) the said loop is left; the programmegoes over from the decision block 116 to the block 74. Now the inputsignals are corrected according to the correction factors in the outputstore. Here, independently of the octave in which the note concernedstands, the correction factor corresponding to this note according toits naming in the output store is used for the correction of this note.Thus a kind of reverse projection to the original multi-octave inputsignal pattern is effected. Since the correction factors state frequencyratios, these are octave-independent. In many usual note signal outputcircuits 22, from the outset a note frequency generator is allocated toeach key 12. In accordance with the invention controllable notefrequency generators are to be provided which, starting from thetempered basic tuning, are automatically retunable by reference to thecorrection factors.

As a result thus a harmonically corrected chord is delivered by the notegeneration device 20 when it has been ascertained that this chordcorresponds to a pre-determined chord pattern. If the chord cannot berecognised, then the chord is produced in the tempered tuning. For thispurpose in the programme loop comprising the blocks 102, 104, 106, 108 asecond loop exit is provided, namely in the decision block 106. If inthe block 106 it is ascertained that on the one hand the played chorddoes not conform with the actual chord pattern (block 104) and on theother hand the highest chord number (for example 39) is reached, thenthe programme goes over from the Block 106 to a block 122, according towhich all correction factors for the output store 62 are set at zerocents.

In a subsequent block 126 the chord store 44 is cleared. Then theprogramme goes over again to the block 74, that is to the output of theinput signals, in this case uncorrected, to the note generation device20. Then the programme returns by way of the "Return Block" 76 to thebeginning of the programme (block 70) again. The entire programme loopcan be run through with a fixed repetition frequency, independently of akey actuation of the instrument.

According to the above thus chord patterns are identified automaticallyand their individual notes are corrected forthwith, so that thedelivered chord sounds harmonically pure. Later-struck individual notesor chords which are constituents of the last-identified chord patternare likewise corrected. It is however also possible to continue andallocate to the individual pattern chords additional chord notes whichare tuned purely in relation to the actual chord notes. If afteridentification of this chord subsequently one of the additional chordnotes is struck, this too is correspondingly corrected.

FIG. 3A carries for example a pattern chord (C-major triad) designatedfor example by α, which is extended upward by an additional chord notelying on the note stage b, at the interval of a large third from theuppermost pattern chord note and downward by an additional chord note(note a) at the interval of a small third. These additional chord notesare symbolised in the chord β in FIG. 3A as sharpened notes. Analternating sequence of large and small thirds results.

The correction factors allocated to these individual notes, incomparison with the tempered tuning, are stated in FIG. 3A on the rightbeside the chord β in cents.

If in the course of playing the chord pattern α is identified, then itsnotes are forthwith corrected too, so that this chord soundsharmonically pure; furthermore if then one or more of the notes of thechord β also containing the additional chord notes are struck, these arein each case harmonically corrected.

                  TABLE I                                                         ______________________________________                                                        Function of the individual notes in                                           the basic position of the chord                                               shown from below upward = from                                                left to right                                                 ______________________________________                                        Major - triad   G T Q                                                         Minor -triad    G M Q                                                         Large third     G T                                                           Small third     G M                                                           Pure fifth      G Q                                                           Small major seventh chord                                                                     G T Q R                                                       Small minor seventh chord                                                                     G M Q R                                                       Large major seventh chord                                                                     G T Q S                                                       ______________________________________                                         Function of the notes in the chord                                            G designates "fundamental note                                                M designates "Small third                                                     T designates "Large third                                                     Q designates "Fifth                                                           R designates "Small seventh                                                   S designates "Large seventh                                              

                  TABLE II                                                        ______________________________________                                        Characteristic of                                                                        Frequency ratio to the fundamental note in                         the note as                                                                              Harmonically pure                                                                             Tempered                                           represented                                                                              as fraction                                                                             in Cents  in Cents                                                                              Tuning                                 ______________________________________                                        G          1          0         0                                             M          6/5       316       300                                            T          5/4       386       400                                            Q          3/2       702       700                                            R          16/9      997       1000                                           S          15/8      1089      1100                                           ______________________________________                                    

    TABLE III              Overall correction Final Frequencies Title of the chord     Function of the     of all chord notes in the chords in proposed for     individual notes of Vibration ratio to Vibration ratio to Correction in     cents Additional correction in cents from cents, related to frequency     Chord pattern No. the chords in basic note G, in cents, note G in cents     from "tempered" to of all chord notes "tempered" to the fundamental     correction im basic position position "tempered" "harmonically pure"     "harmonically pure" in cents "harmonically pure" note G       Major triad  1 Q 700 702 +2  +6 706   T 400 386 -14 +4 -10 390   G 0 0     0  +4 4 Minor triad 4 Q 700 702 +2  -4 696   M 300 316 +16 -6 +10 310     G 0 0 0  -6 -6 Large third 7 T 400 386 -14 +6 -8 392 (duochord)  G 0 0 0      +6 6 Small third 9 M 300 316 +16 -6 +10 310 (duochord)  G 0 0 0  -6 -6     Pure fifth 11 Q 700 702 +2 -1 +1 701 (duochord)  G 0 0 0  -1 -1 Small     major seventh 13 R 1000 997 -3  +1 1001 chord  Q 700 702 +2 +4 +6 706     T 400 386 -14  -10 390   G 0 0 0  +4 4 Small major seventh 17 R 1000 997     -3  +1 1001 chord without fifth  T 400 386 -14 +4 -10 390   G 0 0 0  +4     4 Small seventh chord 20 R 1000 997 -3  -1 999 without third  Q 700 702     +2 +2 +4 704   G 0 0 0  +2 2 Small minor seventh 23 R 1000 997 -3  (-9)0     (991)1000 chord  Q 700 702 +2 -6 -4 696   M 300 316 +16  +10 310   G 0 0     0  -6 -6 Small minor seventh 27 R 1000 997 -3  (-9)0 1000 chord without     fifth  M 300 316 +16 -6 +10 310   G 0 0 0  -6 -6 Large major seventh 30     S 1100 1089 -11  -7 1093 chord  Q 700 702 +2 +4 +6 706   T 400 386 -14     --10 390   G 0 0 0  +4 4 Large major seventh 34 S 1100 1089 -11  -7 1093     chord without fifth  T 400 386 -14 +4 -10 390   G 0 0 0  +4 4  Large     seventh chord 37 S 1100 1089 -11  -7 1093 without third  Q 700 702 +2 +4     +6 706   G 0 0 0  +4 4

    TABLE IIIA              Overall correction Final Frequencies Title of the chord     Function of the     of all chord notes in the chords in proposed for     individual notes of Vibration ratio to Vibration ratio to Correction in     cents Additional correction in cents from cents, related to frequency     Chord pattern No. the chords in basic note G, in cents, note G in cents     from "tempered" to of all chord notes "tempered" to the fundamental     correction im basic position position "tempered" "harmonically pure"     "harmonically pure" in cents "harmonically pure" note G       Small seventh chord 20 R 1000 1018 +18  +9 10009 without third  Q 700     702 +2 -9 -7 693   G 0 0 0  -9 -9 Small minor seventh 23 R 1000 1018 +18      +9 1009 chord  Q 700 702 +2  - 7 693   M 316 316 +16 -9 +7 307   G 0 0     0  -9 -9 Small minor seventh 27 R 1000 1018 +18  +9 1009 chord without     M 300 316 +16 -9 +7 307 fifth  G 0 0 0  -9 -9 Large major seventh 30 S     1100 1088 -12  -6 1094 chord  Q 700 702 +2  +8 708   T 400 386 -14 +6 -8     392   G 0 0 0  +6 6 Large major seventh 34 S 1100 1088 -12  -6 1094     chord without T 400 386 -14 +6 -8 392 fifth  G 0 0 0  +6 6 Large seventh     chord 37 S 1100 1088 -12  -8 1092 without third  Q 700 702 +2 +4 +6 706      G 0 0 0  +4 4

                  TABLE IV                                                        ______________________________________                                                                Screen representations of                                                     "definition octave" and                                                       functions of the "1" on                               Chord Name                                                                              Chord Pattern No.                                                                           the screen                                            ______________________________________                                        Major triad                                                                              1                                                                                           ##STR1##                                                        2                                                                                           ##STR2##                                                        3                                                                                           ##STR3##                                             Minor triad                                                                              4                                                                                           ##STR4##                                                        5                                                                                           ##STR5##                                                        6                                                                                           ##STR6##                                              ##STR7##  7                                                                                           ##STR8##                                                        8                                                                                           ##STR9##                                             Small third                                                                              9                                                                                           ##STR10##                                                      10                                                                                           ##STR11##                                            Pure fifth                                                                              11                                                                                           ##STR12##                                                      12                                                                                           ##STR13##                                             ##STR14##                                                                              13                                                                                           ##STR15##                                                      14                                                                                           ##STR16##                                                      15                                                                                           ##STR17##                                                      16                                                                                           ##STR18##                                             ##STR19##                                                                              17                                                                                           ##STR20##                                                      18                                                                                           ##STR21##                                                      19                                                                                           ##STR22##                                             ##STR23##                                                                              20                                                                                           ##STR24##                                                      21                                                                                           ##STR25##                                                      22                                                                                           ##STR26##                                                      23                                                                                           ##STR27##                                                      24                                                                                           ##STR28##                                                      25                                                                                           ##STR29##                                                      26                                                                                           ##STR30##                                             ##STR31##                                                                              27                                                                                           ##STR32##                                                      28                                                                                           ##STR33##                                                      29                                                                                           ##STR34##                                             ##STR35##                                                                              30                                                                                           ##STR36##                                                      31                                                                                           ##STR37##                                                      32                                                                                           ##STR38##                                                      33                                                                                           ##STR39##                                             ##STR40##                                                                              34                                                                                           ##STR41##                                                      35                                                                                           ##STR42##                                                      36                                                                                           ##STR43##                                             ##STR44##                                                                              37                                                                                           ##STR45##                                                      38                                                                                           ##STR46##                                                      39                                                                                           ##STR47##                                            ______________________________________                                    

                  TABLE V                                                         ______________________________________                                                                     Note examples                                    Chord Name     Chord Pattern No.                                                                           (see FIG. 3)                                     ______________________________________                                        Major triad    1-3           a)                                               Minor triad    4-6           b)                                               Large third (duochord)                                                                       7-8           c)                                               Small third (duochord)                                                                        9-10         d)                                               Pure fifth (duochord)                                                                        11-12         e)                                               Small major seventh chord                                                                    13-16         f)                                               Small major seventh chord                                                                    17-19         g)                                               without fifth                                                                 Small seventh chord                                                                          20-22         h)                                               without third                                                                 Small minor seventh chord                                                                    23-26         i)                                               Small minor seventh chord                                                                    27-29         k)                                               without fifth                                                                 Large major    30-33         l)                                               seventh chord                                                                 Large major    34-36         m)                                               seventh chord                                                                 without fifth                                                                 Large seventh chord                                                                          37-39         n)                                               without third                                                                 ______________________________________                                    

                  TABLE VI                                                        ______________________________________                                                   Number of steps to                                                            left, until first                                                                           following chord                                      For chord pattern                                                                        cell contains a "l'                                                                         is played                                            ______________________________________                                        1          0             C-Major-triad                                        1          1             Cis =                                                                         Des C-Major-triad                                    1          2             D-Major-triad                                        1          3             Dis = Es D-Major-triad                               1          4             E-Major-triad                                        2          0             Gis = As-Major-triad                                 2          1             A-Major-triad                                        2          2             Ais = B-Major-triad                                  2          3             H-Major-triad                                        3          0             F-Major-triad                                        3          1             Fis = Ges-Major-triad                                3          2             G-Major-triad                                        ______________________________________                                    

We claim:
 1. Method of automatically correcting a pitch of a musicalinstrument including a note input device for inputting note inputsignals according to a first intonation system, and a tone generatingdevice for receiving the note input signals and for generatingcorresponding tones, said method comprising the steps of:(i) determiningwhether an input signal pattern comprising at least two note inputsignals corresponds to one of a plurality of predetermined chordpatterns, comprising each a predetermined fundamental note; and (ii) inthe case of correspondence of the input signal pattern to one of aplurality of predetermined chord patterns, replacing the input signalpattern by a corrected input signal pattern, said corrected input signalpattern being determined on the basis of the input signal patterncorrected by first and second correction factors attributed to the onechord pattern, with the first correction factors being determined tocorrect according to a second intonation system different from the firstintonation system, in particular, an intonation system with "just"intonation, all note input signals except for a note input signalcorresponding to the fundamental note of the respective chord pattern,and with the second correction factors being applied to all of the noteinput signals of the input signal pattern with a same correction factorvalue for all of the note input signals, and being determined to shiftall of the note input signals to one of higher and lower signal valuesdependent on whether the first correction factors shift the note inputsignals on average to the one of higher and lower signal values.
 2. Amethod according to claim 1, wherein a second correction factor isdetermined so that a shift of a mean input note signal of the note inputsignals of the input signal pattern is at least partially compensated bythe second correction factor, with the shift being produced only by arespective first correction factor.
 3. A method according to claim 2,wherein the first and second correction factors are indicative ofrelative frequency changes, and wherein the second correction factor ofthe one chord pattern essentially corresponds in value to a mean valueof the first correction factor of the one chord pattern, and correspondsin sign to an opposite of a sign of the mean value.
 4. A methodaccording to claim 1, wherein said determining step includes projectingthe input signal pattern onto a predetermined 12-tone octave andcomparing the input signal pattern with each of the predetermined chordpatterns defined within the octave.
 5. A method according to claim 4,comprising the step of shifting the input signal pattern within the12-tone octave, as a whole, in a first direction by half-note stepsuntil a signal of the input signal pattern is present at a predeterminedend of the 12-tone octave, wherein a number of first shift steps neededfor the shift are counted, and wherein the shifted input signal patternis compared with the predetermined chord patterns, with thepredetermined chord patterns likewise comprising a chord pattern note atthe predetermined end of the 12-tone octave.
 6. A method according toclaim 5, comprising the steps of loading, in the case of conformity ofthe input signal pattern with one of the predetermined chord patterns, acorrection signal pattern corresponding to the one chord pattern into a12-tone output store, and shifting the correction signal pattern, as awhole, in a second direction by half-note steps within the output storefor a number of second shift steps, with the number of second shiftsteps being equal to the number of first shift steps and with a secondshift direction being opposed to the first shift direction.
 7. A methodaccording to claim 6, wherein each of the correction signals of thecorrection signal pattern comprises the first and second correctionfactors.
 8. A method according to claim 6, wherein the correctionsignals of the correction signal patterns define relative frequencychanges.
 9. A method according to claim 5, comprising the step ofshifting each of the predetermined chord patterns cyclically within the12-tone octave, as a whole, in a third shift direction by half-notesteps, wherein after each step, the input signal pattern is comparedwith the one chord pattern, wherein the shifting is ended whenconformity between the unshifted input signal pattern and the one of thechord patterns is reached, and wherein a number of third shift steps isneeded until conformity is reached, is counted.
 10. A method accordingto claim 9, comprising the steps of loading, in the case of conformityof the input signal pattern with the one chord pattern, a correctionsignal pattern corresponding to the one chord pattern into a12-tone-output store, and cyclically shifting the correction signalpattern, as a whole, in a fourth shift direction by half-note stepswithin the output store for a number of fourth shift steps, the numberof fourth steps being equal to the number of third shift steps, and thefourth direction being opposite to the second direction.
 11. A methodaccording to claim 10, wherein the correction signals of the correctionsignal patterns each comprises the first and second correction factors.12. A method according to claim 11, wherein the correction signals ofthe correction signal patterns define relative frequency changes.
 13. Amethod according to claim 1, comprising the step of checking, afterdetermining a correspondence of the note input signal pattern with oneof the chord patterns, following input signal patterns, whether at leastone note of the following input signal pattern corresponds to arespective note of the one chord pattern, wherein, in case of acorrespondence, the at least one note of the following input signalpattern is corrected by the same first and second correction factors asa respective note of the one chord pattern.
 14. A method according toclaim 1, comprising the step of comparing, in the case of a multimanualinput device, input signal patterns of respective input devicesseparately with chord patterns of the predetermined chord patterns. 15.A method according to claim 14, comprising the step of checking, afterdetermining the correspondence of an input signal pattern of one of theinput devices with one of the chord patterns, the following input signalpatterns of all input devices whether at least one note corresponds to arespective note of the one chord pattern, wherein in the case of acorrespondence, the at least one note of the following input signalpattern is corrected by the same first and second correction factors asthe respective note of said one chord pattern.
 16. A method according toclaim 1, comprising the step of comparing only input signal patterns,which correspond to chord patterns having at least three differentnotes, with the chord patterns of the plurality of predetermined chordpatterns.
 17. A method of automatically correcting a pitch of a musicalinstrument including a note input device for inputting note inputsignals according to a first intonation system, in particular, anintonation system with equal temperament and a tone-generating devicefor receiving the note input signals and for generating respectivetones, the method comprising the steps of:(a) determining whether aninput signal pattern, comprising at least two note input signals,corresponds to one of a plurality of predetermined chord patterns eachcomprising a predetermined fundamental note; (b) in the case of acorrespondence of the input signal pattern to one of the plurality ofchord patterns, replacing the corresponding input signal pattern by acorrected input signal pattern, the corrected input signal pattern beingdetermined on a basis of the input signal pattern corrected by first andthird correction factors, the first correction factor being attributedto the one chord pattern and being determined to correct, according to asecond intonation system, different from the first intonation system, inparticular an intonation system with "just" intonation, all note inputsignals except for a note input signal corresponding to the fundamentalnote of the respective chord pattern; (c) determining whether twosuccessive input signal patterns, first and second signal patterns,correspond to two different chord patterns of the plurality ofpredetermined chord patterns but with at least one coinciding note; and(d) in case of the correspondence of the two successive input patternsto two different chord patterns, further correcting the second inputsignal pattern over the two successive input patterns by the thirdcorrection factor, the third correction factor being determined to shiftat least the at least one coinciding note within the second input signalpattern so that a frequency difference between the coinciding notes ofthe first and the second input signal patterns is less than apre-determined difference value.
 18. A method according to claim 17,wherein said predetermined difference value is 8 cents.
 19. A pitchcontrol system for a musical instrument comprising, (i) at least oneinput device for inputting note input signals according to a firstintonation system, in particular, an intonation system with equaltemperament; (ii) a tone generating device for receiving the note inputsignals and for generating respective tones; (iii) a chord recognitioncircuit for determining whether an input signal pattern comprising atleast two note input signals corresponds to one of a plurality ofpredetermined chord patterns, each of said predetermined chord patternscomprising a predetermined fundamental note; (iv) a correction signalpattern store circuit for storing correcting factors attributed to eachof the predetermined chord patterns; (v) a correction circuit forreceiving the input signal pattern and the correction signals forgenerating output signals to be received by the tone-generating device,which output signals correspond to the input signals corrected accordingto the correction signals; and (vi) a control circuit connected to thechord recognition circuit, the correcting signal pattern store circuitand the correction circuit for causing the correction signal patternstore to deliver the correcting factors attributed to one of saidpredetermined chord patterns to the correction circuit in case that thechord recognition circuit determines the correspondence of said onechord pattern with the present input signal pattern.
 20. A pitch controlsystem according to claim 19, wherein said correction signal patternstore is provided for storing first and second correction factors, thefirst correction factor being determined to correct, according to asecond intonation system, in particular an intonation system with "just"intonation, all note input signals except for that note input signalcorresponding to the fundamental note of the respective chord pattern,and said second correction factor being determined to shift all noteinput signals to one of higher and lower signal values according towhether the first correction factor shifts the note input signals onaverage to the one of lower and higher signal values, respectively. 21.A pitch control system according to claim 19, further comprising anoctave store having 12 storage places attributed to each note of apredetermined 12-tone octave for storing an input signal pattern, withnotes of the input signal pattern being projected into the 12-toneoctave by 12-tone shifts if laying outside of the predetermined 12-toneoctave.
 22. A pitch control system according to claim 21, comprising awork store having 12 storage places for receiving a signal content ofthe octave store, the signal content of the work store being shiftableby one-storage-place steps in a predetermined direction, with a numberof shift steps being counted by a shift counter.
 23. A pitch controlsystem according to claim 21, comprising a chord pattern store with aplurality of storage lines each provided with 12 storage places, eachline being attributed to one of the predetermined chord patterns.
 24. Apitch control system according to claim 23, comprising a chord storehaving 12 storage places attributed to each note of an octave for thestorage of a last determined chord.
 25. A pitch control system accordingto claim 23, comprising a correction factor store with storage linesprovided each with 12 storage places allocated to each note of anoctave, each storage line being attributed to one of the predeterminedchord patterns.
 26. A pitch control system according to claim 25,comprising an output store with 12 storage places for receiving acontent of the storage line attributed to a determined chord within thecorrection factor store, each storage content being shiftable inon-storage-place steps.